Recommended RAID BLOCK size for Mac HDD's

[Johnny Friday]

Hi all,
setting up a new mac pro for editing and storage. I am raiding two (2)TB Hitachi 7200rpm 32mb cashe HDD's and here is my system:

Mac Pro
dual 2.26 quad core
32gig ram

HDD's:
1TB holding software
two 2TB HDD's Raided (raid 0)
one 2TB HDD

**the above is all in my MacPro**

Attached is a serial enclosure 5 bay drive with five 2TB seagate 5900rpm drives with port multiplier.

So...my question is actually for my two 2tb drives i am raiding that are installed in my MacPro:
*after setting up the two HDD's for raid, i'm asked what RAID BLOCK size i would like.

**Any suggestions for me? I have these options:
32k
64k
128k
256k

Thanks for any help on this...I am assuming higher is better, but i must be giving up something if i go to 256k.

Any advise or thoughts are appreciated.
thanks
JOhnny

 

[Craig Schober]

i always choose 256k. if you're storing video, your block sizes need to be on the larger size because of the nature of video file sizes. i don't think you'll be giving up too much space vs. 32k blocks though i'm not sure if you're getting any better performance either...just the way i've read to set up raids for video.

 

[Jeff Kilgroe]

In that sort of array, the block size isn't going to make any real difference. Default is 32K, I typically use 64K blocks on the software RAIDs in a Mac. No real reason, just habit. And I haven't seen any performance advantages to using higher block sizes in these software arrays. You'll do yourself more good by making your RAID-0 out of three drives instead of two, unless you have a specific use for that last remaining drive.

Why 32GB RAM? That's cool, but not too many ways to use it all.

 

[Johnny Friday]

i actually set it for 256k and using only 2 hdd's but I can easily go to 3 hdd's and raid them zero...but why is three so much better than one? i understand it is writing to all three, but then we could say why not 4,5 etc..... But is there a magic number with three hdd's at raid zero?

as for why 32gigs of ram....well, i have NO IDEA. but keep reading on the boards that i do myself much better to have more ram than to worry about going to a larger processor like the 2.66 is it or 2.93....i keep seeing on the boards, go with more RAM...So, figured 32gigs would be good for so much video. Now you have me asking why is 32gigs not ideal....is there a top out number for RAM for video or ideal amount? So i'll never use my 32gigs?

Well, it was only $1300 and not $5k + like apples. Got it from OWC.
Thanks for your reply and questions i have here.

 

[Charles Angus]

i actually set it for 256k and using only 2 hdd's but I can easily go to 3 hdd's and raid them zero...but why is three so much better than one? i understand it is writing to all three, but then we could say why not 4,5 etc..... But is there a magic number with three hdd's at raid zero?

as for why 32gigs of ram....well, i have NO IDEA. but keep reading on the boards that i do myself much better to have more ram than to worry about going to a larger processor like the 2.66 is it or 2.93....i keep seeing on the boards, go with more RAM...So, figured 32gigs would be good for so much video. Now you have me asking why is 32gigs not ideal....is there a top out number for RAM for video or ideal amount? So i'll never use my 32gigs?

Well, it was only $1300 and not $5k + like apples. Got it from OWC.
Thanks for your reply and questions i have here.

In RAID 0, more drives = more speed, but also more chance of failure. Remember, with RAID 0, a failure of any drive will destroy all information on the entire array.

 

[Jeff Kilgroe]

That's how I have my Mac Pro systems configured. 1 drive for system / apps, the remaining 3 drives in RAID-0. Just have a good backup solution in place. I actually haven't lost a HDD in RAID-0 in a Mac Pro <knock wood>. But I've lost tons of HDDs to failure over the years, lately I've had a bad run of luck with 1.5TB Seagates that I was for a while to run in a couple external RAIDs. Anyway, with 3 x 1TB HDDs, you should be able to handle 2K DPX in realtime, or real close. It's just a performance thing.

Having the full 32GB RAM in one of these systems isn't a bad thing by any means. You just won't find it easy to use all of it. Most all applications are still 32bit, which means they each can only use 2~3GB max at a time. 16GB is a real sweet spot amount for the Mac Pro, seems to cover all the bases most of the time. I can max it out if I specifically try to do so. As more apps go 64bit we could see expanded RAM usage and the desire for higher memory capacities will increase.

 

[Johnny Friday]

makes sense to have 3HDD's to run 2k realtime dpx....i have not yet tried w/the two HDD's i have, but that is essentially what i would like to see....realtime 2k. Now my backup is quite sweet i think. 2 sata enclosures with five 2TB drives in them w/port multiplier. Basically these are standalone drives---no raids, all hot swappable and merely to back up as storage of my stock footage. Backup twice on an HDD and store them is what i do...all new, but is working for now.

Thanks Jeff

 

[Kaku Ito]

For our DIT onset Mac Pro, I use Caldigit RAID Card for the internal 4-bay formatted at RAID5 and additional boot drive installed in the second optical drive bay with 5" to 3.5" drive adaptor. For larger data transferring, I set the block size at 256k all the time.

 

[Imran Farouk]

If i remember rightly RAM tops out at 16GB, maybe wrong but at least thats what I remember, I've got about 16GB in mine, didn't see a need for 32GB right now, its good tho to have for the future instead of deciding to expand later

EDIT:
Only because later maybe more expensive...don't know if you got yours on a deal or not...was just a thought

 

[Greg M]

CalDigit RAID Card wont work on new Macs...only option is Apple.
They changed the internal connector.

 

[Will Keir]

Well I'm glad you asked this question some four years back Johnny because here I am with the same question, though none of the answer here were definitive. Since I'm editing Dragon footage, I'm setting my RAID block size to 256k.

If anyone can add why 256k might be better than 32k or that it doesn't really matter, if might be helpful for the next user down the line.

Thanks.